Piezoelectric materials are widely used in various electronic devices, for example the optical zooming technique recently used in camera lenses is a high actuating force that utilizes piezoelectric materials.
Referring to FIG. 1A, shown is a driving structure 1 developed by Konica-Minolta Inc. using the principle of a smooth impact drive mechanism (SIDM). The driving structure 1 includes a retaining mount 10, a piezoelectric material 11 fixed to the retaining mount 10, a frictional rod 12 attached to the piezoelectric material 11, and a corresponding shifting element 13 sheathing the frictional rod 12. The piezoelectric material 11 is electrically connected to a power (not shown). The voltage of the power changes periodically. When there is a voltage, the piezoelectric material 11 swells; when the voltage disappears, the piezoelectric material 11 restores to its original shape. Such moving mechanism causes the frictional material 12 to deform and actuate the shifting element 13 to shift along the frictional rod 12.
Referring to FIG. 1B, the driving structure 1 is combined with a lens module 14. The lens module 14 includes a first lens 140, a second lens 141 and a third lens 142. The second lens 141 is disposed between the first lens 140 and the third lens 142. The driving structure 1 is attached to the second lens 141 via the shifting element 13. The retaining mount 10 is fixed to a housing (not shown) encasing the lens module 14. When the power is supplied to the piezoelectric material 11, the shifting element 13 shifts along the frictional rod 12, causing the second lens 141 to move between the first and third lenses, thereby achieving optical zooming.
As can be seen from the drawing, the piezoelectric material 11 has a cross-sectional area slightly smaller than that of the retaining mount 10, but slightly bigger than that of the frictional rod 12. Such a design ensures the piezoelectric material 11 is in complete contact with the retaining mount 10 and the frictional rod 12 is in complete contact with the piezoelectric material 11, so that kinetic force can be integrally transferred to the frictional rod 12. However, this may lead to the problem of insufficient stability due to contact faces between elements being too small. In additional, the retaining mount 10, the piezoelectric material 11 and the frictional rod 12 must be symmetrical with respect to a common interlarding axis in order to have standardized specifications, so precision of alignment during the manufacturing process is required. When applying to small electronic devices such as a mobile phone, the driving structure 1 must be reduced and a more precise aligning technique must be employed to achieve the symmetrical structure. Moreover, the cross-sectional areas of the retaining mount 10, the piezoelectric material 11 and the frictional rod 12 are all cylindrical, which is rather difficult to manufacture and may increase the cost of manufacturing.
Furthermore, when applying to small electronic devices, the piezoelectric material 11 must be reduced in proportion, which may have the problem of insufficient kinetic force.
In addition, the frictional rod 12 would gradually wear out and be rendered unusable in the long term due to friction with the shifting element 13. In this case, since the frictional rod 12 is fixed to the piezoelectric material 11 and the second lens 141, the whole driving structure 1 and the second lens 141 need to be replaced.
Moreover, since the driving structure 1 is cylindrical, so it cannot be completely adhered to the housing of the electronic device. In order to fasten the retaining mount 10, an additional component is required in the housing to encase the retaining mount 10 while being fixed to the housing so as to fasten the driving structure. Consequently, more space is occupied in the electronic device.
Furthermore, as for the design of the structure developed by KONICA-MINOLTA Inc., all the components are sequentially installed on the same axis, which would result in a long length that presents a problem when applying to a small device such as a mobile phone. In result, the mobile phone is still thick as usual, and is contradictory to the trend toward thin and compact appearance of the portable electronic devices.
Therefore, there is a need for a solution that addresses and solves the abovementioned shortcomings of the prior art.